The present invention relates to footwear and, more particularly, to footwear that promotes the natural movement of the wearer's foot and conformity to the ground.
Conventional footwear typically includes two primary elements: an upper and a sole construction. The upper at least partially covers the wearer's foot, and the sole construction provides support for the wearer's sole. The sole construction can include multiple layers and materials. For example, conventional sole constructions can include a molded foam midsole over a natural rubber outsole. The molded foam midsole can provide cushioning while the natural rubber outsole can provide traction and wear resistance.
Conventional sole constructions are primarily flexible in a single direction. In particular, many sole constructions are intended to flex in the upward direction, in which the ground engaging surface of the outsole is convex. Flexibility of this kind is typically achieved with modifications to the outsole. For example, it is known to introduce grooves in the outsole to promote the bending of the outsole in the upward direction. It is also known to separate the outsole into individual components that move away from each other as the outsole is bent in an upward direction.
The natural movement of the wearer's foot is not limited to flexure in the upward direction, however. In addition to upward flexure, or dorsi-flexion, the human foot naturally exhibits downward flexure, or plantar-flexion. Conventional sole constructions typically exhibit significant resistance to plantar-flexion, however. For example, many conventional sole constructions include an outsole or a midsole that resists plantar-flexion of the wearer's foot. By opposing the natural ability of the human foot to flex downwardly, many such sole constructions compromise stability and grip on all but even surfaces.